1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus that scans a tested body pressed by a probe and an image display method thereof.
2. Description of the Related Art
In recent years, a diagnosis (hereinafter, referred to as a blood vessel echo) of a blood vessel using an ultrasonic wave is being widely performed. In the blood vessel echo, the existence of an intravascular thrombus or vascular stenosis and occlusion are diagnosed for various parts, such as a carotid artery, a main artery, a coronary artery, a peripheral artery, and a peripheral vein.
There is a deep vein thrombosis (hereinafter, referred to as a ‘DVT’) as a disease related to a thrombus. The DVT is a disease causing a thrombus to be formed in a deep vein. Most of the thrombi are generated in a leg. The formed thrombus may peel and fall from a blood vessel wall. Such a thrombus that peels and fall is called an embolus. The blood of a leg vein passes through the heart and flows to a lung. For this reason, an embolus generated in the leg vein may be blocked in the artery of the lung after passing through the heart, which causes pulmonary embolism. That is, the thrombus formed in the leg vein may serve as a source of embolus of pulmonary embolism.
In order to prove the existence of a thrombus, the thrombus may be visualized on an ultrasonic image or disappearance of a Doppler signal related to a venous blood flow may be checked. In addition, the venous blood pressure of a blood vessel of a vein (for example, a femoral vein or a popliteal vein) near a body surface is low if the blood vessel is not occluded. Accordingly, the blood vessel deforms easily when the body surface is pressed with a probe. On the other hand, in the case when the blood vessel is not occluded, the blood vessel does not deform even if the body surface is pressed. Therefore, the existence of a thrombus can be determined by checking whether or not a blood vessel is deformed by pressure.
In recent years, the following techniques useful for determining whether or not a blood vessel deforms when pressing a tested body are disclosed.
1. A blood vessel moves when a tested body is pressed. A technique of tracing a part moving on an ultrasonic image, which is useful in such a case (for example, refer to JP-A-2003-175041).
2. A probe having a pressure sensor provided on a contact surface being in contact with a tested body, which is useful in the case of measuring a pressure value when pressing the tested body (for example, refer to JP-A-2003-225239).